One of the ways to extract geothermal heat from the Earth’s crust is through Deep Borehole Heat Exchangers (DBHE). These can be either drilled especially for a heat extraction or, more cost-effectively, reconstructed from already-existing, negative, or abandoned oil or natural gas wells.
Borehole heat exchangers allow an exchange of geothermal heat between rock formation and heat carriers, circulating in the closed-loop system between the surface and an underground reservoir. The heat can be supplied directly, for instance from deeper wells with higher geothermal gradient, or indirectly using heat pump systems. During reconstruction operations of an already-existing well, the inner column is the most important feature, which in large part determines the overall success of the DBHE investment. Other properties include already existing well construction and characteristic of an underground rock mass.
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Potential application of vacuum insulated tubing for deep borehole heat exchangers, by Tomasz Śliwaa; Michał Kruszewskiab; Alireza Zarec; Mohsen Assadic; Aneta Sapińska-Śliwaa. Geothermics, Volume 75, September 2018, Pages 58-67. https://doi.org/10.1016/j.geothermics.2018.04.001
Potential application of vacuum insulated tubing for deep borehole heat exchangers, by Tomasz Śliwaa; Michał Kruszewskiab; Alireza Zarec; Mohsen Assadic; Aneta Sapińska-Śliwaa. Geothermics, Volume 75, September 2018, Pages 58-67. https://doi.org/10.1016/j.geothermics.2018.04.001